The only reason Man has two operaters is that BA offer a transfer system between flights, where as Euromanx don't. I.E. you can buy a ticket with BA and SA or VS and book your bags through, with Lpl being a lowcost airport the transfer system is not used.
Once BA connect go, not to sure if there will be 2 operaters into Man anymore because EMX and BE seem to be very close atm....